Add Screen Off option for buttons double-tap/long press (1 of 2)

This is being done primarily to replicate functionality on find7 Color OS.
Would it be better/possible to have this change only effect the find7?

Change-Id: I7e0c21b174b9cdd020c8d27c91c4c72201e228ff

Conflicts:
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java